As a newbie coming in to the series, I have to admit that my favorite parts of the game are the sounds. Unlike traditional games, where you'd have music constantly playing in the background or the sounds of gun fire, Portal 2 has nothing. For most of the game, there's just the dull hum of equipment depending where you are or you'll hear nothing.
If the thought of a game that doesn't have background noise or even music playing underneath makes you want to shy away, don't. While Portal 2 doesn't make a huge splash in the gaming sounds market, it does make its sounds through the voice acting. While the lead character doesn't speak, there's plenty of funny, quirky, and disturbing dialogue that's going on around you.
By far, the best comes from that of Aperture Science CEO, Cave Johnson, who is voiced by JK Simmons. Even when I watched friends play the game, some of the things Cave said usually made me go "what?". These usually pop up as you are first exploring the testing facility; this line actually made me say, "awesome!"
Those of you helping us test the repulsion gel today, just follow the blue line on the floor. Those of you who volunteered to be injected with praying mantis DNA, I've got some good news and some bad news: bad news is we're postponing those tests indefinitely. Good news is we've got a much better test for you: fighting an army of mantis men. Pick up a rifle and follow the yellow line. You'll know when the test starts.
Another great batch of quotes from GLaDOS, who is once again voice by Ellen McLain. Again, as someone who has not played the series or knew of the game, most of what she says at the beginning made me ask, "Why is she so mad at me?" until finally I started asking, "What is wrong with you!?"
Don't let that "horrible person" thing discourage you. It's just a data point. If it makes you feel any better, science has now validated your birth mother's decision to abandon you on a doorstep.
Don't even get me started on the Cave/GLaDOS conversation about lemons. That by far disturbed me. Hilarious, but disturbing.
There's also the great voice talent of Stephan Merchant. If you're fans of the Ricky Gervais Show, you'll recognize Merchant as one of the members of the funny trio (the others being Gervais and Carl Pilkington), as well as appearing in some of Gervais' movies; he is also one of the co-writers and co-directors for the original British version of The Office. Here, he lends his voice to Wheatley, your helpful little AI friend who is first introduced after you've discovered where you've been for several years. He's your companion and helpful sidekick until you meet your first boss.
And if those things don't get you, you not only have some of the chatter from other AIs that are stuck in this facility with you, but as with the first game, GLaDOS leaves you a little party gift when you complete the game - a song! Interestingly enough, McLain is an accomplished opera singer who sings not only the ending songs for both games, but that of a special performance by the turrets at the end of the game.